Atrioventricular block following prolonged focal cryoablation for parahisian premature ventricular complexes

A 54-year-old woman with symptomatic premature ventricular contractions (PVC) was referred for electrophysiological study. The earliest activation was located at the parahisian area, so it was decided to ablate using cryoenergy. No AV conduction impairment was observed during cryomapping. PVCs were abolished after the first 15 seconds of cryoablation, without recurrence. However, after 354 seconds of cryoablation, a mild PR prolongation was followed by first degree and 2-to-1 AV block. Termination of cryoablation led to complete recovery without definitive damage and with elimination of the PVC. This case illustrates how lesion formation using cryoenergy can continue to evolve even after several minutes, highlighting the need of monitoring throughout the whole target duration.